Dynamic Cache Management in Storage Devices

1. A method for dynamic cache management in a hard disk drive, the method comprising: receiving data to write to the hard disk drive; determining that data is being written to a cache zone of the hard disk drive at a rate that is faster than or equal to a predefined threshold rate; responsive to the determining, increasing a size of the cache zone and decreasing a size of a storage zone of the hard drive; writing the received data to the cache zone of the hard disk drive using a perpendicular magnetic recording format; and migrating the received data from the cache zone to the storage zone of the hard disk drive, wherein the migrated data is written to the storage zone of the hard disk drive using a shingled magnetic recording format.

2. The method of claim 1 , further comprising: determining, subsequent to the migrating the received data, that data is being written to the cache zone of the hard disk drive at a rate that is slower than or equal to a second predefined threshold rate; and decreasing the size of the cache zone.

3. The method of claim 1 , wherein the predefined threshold rate is defined as a percentage of the size of the cache zone written within a specified time period.

4. The method of claim 1 , further comprising: determining that the hard disk drive has dynamic cache support, the determining comprising inspecting a value in a firmware of the hard disk drive; and configuring the hard disk drive, the configuring comprising: setting an initial size of the cache zone of the hard disk drive; and specifying the predefined threshold rate.

5. A method comprising: storing data in a first region of a storage device in a first storage format; storing data in a second region of the storage device in a second storage format, wherein the second storage format is different from the first storage format; and dynamically changing a ratio between a size of the first region and a size of the second region based on a determining that data is being written to the first region at a rate that is faster than a specified threshold rate, wherein the dynamically changing the ratio between the size of the first region and the size of the second region comprises increasing the size of the first region and decreasing the size of the second region.

6. The method of claim 5 , wherein the dynamically changing the ratio between the size of the first region and the size of the second region comprises: increasing the size of the first region by an increment size; and decreasing the size of the second region by the increment size.

7. The method of claim 5 , further comprising: subsequently determining that data is written to the first region at a rate that is slower than than or equal to the specified threshold rate; and decreasing the size of the first region.

8. The method of claim 5 , wherein the detecting comprises: monitoring data writes to the first region of the storage device; determining the rate at which the data is written to the first region based on the monitored data writes; and comparing the determined rate to the specified threshold rate.

9. The method of claim 5 , wherein: the storing data in the first region of the storage device comprises receiving data and buffering the received data in the first region; and the storing data in the second region of the storage device comprises moving the buffered data from the first region to the second region.

10. The method of claim 5 , further comprising: configuring the storage device, the configuring comprising: setting an initial size of the first region of the storage device; setting an initial size of the second region of the storage device; and specifying a criterion for dynamically changing the ratio between the size of the first region and the size of the second region based on the rate at which data is written to the first region.

11. A system comprising: a computer-readable storage medium comprising: a cache zone wherein data is stored in a first storage format, and a storage zone wherein data is stored in a second storage format, wherein the second storage format has a larger storage capacity than the first storage format; a storage device controller configured to: receive requests to write data to the computer-readable storage medium, write the received data to the cache zone of the computer-readable storage medium in the first storage format, and move the cached data from the cache zone to the storage zone, wherein the moving comprises writing the moved data to the storage zone in the second storage format; and a dynamic cache manager configured to: determine that a rate of data placement in the cache zone is faster than a specified threshold rate, and responsive to the determining, dynamically change a size of the cache zone on the computer-readable storage medium, wherein the dynamically changing the size of the cache zone comprises increasing the size of the cache zone on the computer-readable storage medium and decreasing a size of the storage zone on the computer-readable storage medium.

12. The system of claim 11 , wherein the dynamically changing the size of the cache zone on the computer-readable storage medium comprises: changing the size of the cache zone over time to transform the computer-readable storage medium from a lower-capacity storage medium with a higher random access write performance into a higher-capacity storage medium with lower random access write performance.

13. The system of claim 11 , wherein the computer-readable storage medium comprises a magnetic disk.

14. The system of claim 13 , wherein the cache zone of the computer-readable storage medium comprises an outermost circular track of the magnetic disk.

15. The system of claim 11 , wherein: the first storage format is a perpendicular magnetic recording format; and the second storage format is a shingled magnetic recording format.

16. The system of claim 11 , wherein the dynamic cache manager is further configured to: determine that the rate of data placement in the cache zone is slower than the specified threshold rate for a specified period of time, and responsive to the determining, decrease the size of the cache zone on the computer-readable storage medium.

17. The system of claim 11 , wherein the storage device controller is configured to move the cached data from the cache zone to the storage zone when an amount of data stored in the cache zone is equal to a capacity of the cache zone.

18. The system of claim 17 , wherein the moving the cached data from the cache zone to the storage zone comprises: tracking write accesses for blocks of data stored in the cache zone; and moving a block of data with a fewest number of write accesses, compared to other blocks of data stored in the cache zone, from the cache zone to the storage zone.

19. The system of claim 11 , wherein the storage device controller is implemented in a hardware component of the computer-readable storage medium.